The present invention relates to an apparatus for separating a sponge iron product from the discharge material of a rotary furnace by screening the sponge iron product from the discharge in a hot condition and in the absence of air.
A rotary furnace generally discharges a mixture of sponge iron, excess coal, desulfuring agent and ash at temperatures between 800.degree. and 1100.degree. C. In the usual prior art processing apparatus the discharge is cooled in a cooling drum to temperature between 80.degree. and 150.degree. C. by indirect and direct water cooling. The sponge iron is then separated from the accompanying non-magnetic materials usually by sifting and subsequent magnetic separation. The cold sponge iron is then fed into an electric furnace for further processing.
A major disadvantage of the prior art apparatus is that the cooling of the sponge iron results in a considerable amount of energy loss since the sponge iron must be heated in an electrical furnace after separation. Although it has long been sought to avoid this drawback, a hot charging of sponge iron into the electrical furnace has been used in practice only for products produced in a shaft furnace by reduction with gases where thus separation or other subsequent treatment of the intermediate product was not required.
Several proposals for the hot screening of the discharge from a rotary furnace have become known which, however, have not been accepted in practice because of the rapid breakdown of the apparatus due to severe wear. Such an apparatus is disclosed, for example, in German Pat. No. 1,215,937, where the input end of a cooling drum following the rotary furnace includes a screening drum arranged in a manner that only the material passing through the screen can enter the cooling drum and material that has not passed through the screen is discharged into an after-connected processing assembly. It is a significant disadvantage of this and other prior art devices that the entire rotary furnace system must be shut down, regardless of whether there occurs a malfunction in the separating apparatus due to high loads or a malfunction in the after-connected melting assembly. Having to shut down the entire system proves to be extremely costly.